If you’r going to have a C

If you’r going to have a CGI character, than I assume that you have some short of 3D animation software. If the object that you need to put the CGI behind is stationary, than you could set up a non-rendered object, that is the shape of the in-video object, so that when you composit in video, the rendered CGI eliments would be blocked out by the non rendered object, and it should intermingle pretty cleanly.